GB563955A - Improvements in scavenging systems for two-stroke-cycle internal combustion engines - Google Patents

Abstract

563,955. Two-stroke engines ; inlet and exhaust systems. BUTLER, J. F., PURDAY, H. F. P., MICKELSEN, V., and REBBECK, SIR F. E. June 5, 1944, No. 3776/43. [Class 7 (ii)] In a two-stroke engine in which a scavenging system is arranged to utilize the energy of the exhaust gases to induce a fresh charge into the cylinders, a scavenge chamber e surrounding or adjacent to piston-controlled ports f or valves in one or more engine cylinders is connected to an induction passage d whose " effective volume " is not less than the square of the cylinder volume divided by the sum of the volumes of the cylinder and the chamber e. A mathematical expression for the " effective volume " is given. The passage d is connected to the atmosphere or to a chamber c in communication with the outlet of a positive-displacement, centrifugal or axial blower a. In the system shown diagrammatically in Fig. 1, the system includes exhaust valves h and pipes j, chamber k and outlet pipe m, the " effective volume " of the exhaust pipes being of the same order as, or larger than, the cylinder volume. Each pipe. d and chamber e may supply one or several cylinders, there being an exhaust pipe j to each cylinder and a chamber k and pipe m common to all-the cylinders or to a group of cylinders. In the construction shown in Fig. 4, chambers 5 around the inlet ports 6 of two pairs of cylinders are supplied with air from a blower through a pipe 2, chamber 3 and helical passages 4 around the chamber 3. The exhaust from valves in the cylinder head passes through similar helical passages to an exhaust chamber and outlet pipes &c. In a modification, Fig. 5, chambers 15 around the inlet ports 16 are supplied from the air chamber 11 through pipes 12, 13 having guide plates 14 in their bends. The diameters of the pipes 12, 13 are different, to correspond to the different number of cylinders 17 fed from the chambers 15. In a further form, Fig. 6, chambers around the inlet ports are supplied from the air chamber 20 through pipes 21 coiled in a plane parallel to the longitudinal axis of the engine.